(1) Field of the Invention
This invention relates to a waterproofed connector in which a cable outlet of a connector housing is coupled to a mold resin layer.
(2) Statement of the Prior Art
A bayonet molded plug which is a kind of connector having a molded cable outlet is known by, for example, Japanese Utility Model Public Disclosure No. HEI 5-73871 (1993). This bayonet molded plug is produced by attaching a pair of bayonet terminals to a mold core made of a thermosetting resin, connecting an end of each core wire of an electrical cable to each terminal, and molding the core wires and mold core by a thermoplastic resin. Such structure has the advantage of enhancing waterproofing and impact strength since exposed core wires are covered with a resilient mold resin layer.
However, various problems on forming are caused when the above mold structure is applied to a connector in which terminal metal fixtures are accommodated in a cavity within a connector housing. If the cable outlet of the connector housing is molded merely by a mold resin, the mold resin will enter the cavity by an injection pressure upon forming, so that the mold resin will reach an interior of a connection part of the terminal metal fixture. In order to prevent such leakage, it is necessary to seal one end of the cavity. However, it is difficult to effect sealing of the cavity at its end, since the injection pressure of the mold resin will become substantially higher and the core conductors pass through the end of the cavity. If the injection pressure is lowered to prevent the leakage of the mold resin, the efficiency of production will be reduced.
On the other hand, in the case of a molded type connector having such structure requiring a better waterproofing function, the cost of production will be abruptly increased for the following reasons:
In such molded type connector, entering paths of water in question are a boundary space between a mold resin layer and a sheath of an electrical cable and a boundary space between the mold resin layer and a connector housing.
Boundary portions between mold resin parts are likely to have difficulties in adherence to each other when they have a poor appetency and cause a gap therebetween on account of differences of thermal expansion and contraction during a cooling process on molding or a change of temperature while in use. Accordingly, it is necessary to select a resin material which has a good appetency to a sheath resin of the electrical cable and a mold resin of the connector housing and a low coefficient of thermal expansion.
However, the sheath resin of the electrical cable is polyethylene, crosslinking polyethylene, or fluorocarbon polymer while the connector housing is made of PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide). Thus, both materials are generally different. It is difficult to select a mold resin suitable for both resins. Consequently, an expensive mold resin is inevitably selected and materials of the sheath resin of the electrical cable and the connector housing must be reconsidered.